1. Field of the Invention
The present invention relates to the field of displaying technology, and in particular to a polysilicon manufacturing method that enhances homogeneity of polysilicon layer.
2. The Related Arts
The displaying technology has been under fast development recently. A flat panel display device is significantly different from a traditional video image displaying device by adopting totally different displaying and manufacturing technology. The traditional video image displaying device is generally based on a cathode ray tube (CRT), from which a flat panel display device differs primarily concerning changes made in respect of weight and size (thickness). Generally, a flat panel display device has a thickness not greater than 10 centimeters, among the other differences associated with various technical aspects, such as theory of displaying, manufacturing material, manufacturing process, driving for displaying video images.
The flat panel display device possesses features such as being completely flattened, being light and thin, and energy saving and currently undergoes progresses toward high PPI (pixels per inch), low power consumption, and high integration. Amorphous silicon, which is conventionally used, due to inherent limitation, cannot suit the above described needs and polysilicon is considered the best candidate for substituting amorphous silicon for polysilicon is fit for the needs for future developments of the flat panel display device. Thus, low-temperature polysilicon (LTPS) displaying technology has become a new favorite of the displaying field.
As links of the technical cores of the low temperature polysilicon displaying technology, the manufacturing process and material behavior of polysilicon determine the performance of a display device. The manufacturing processes of polysilicon that are currently known include: low pressure chemical vapor deposition (LPCVD), solid phase crystallization, metal induction, and laser annealing. The most commonly used process in the industry is the laser annealing operation, which uses the high temperature generated by a laser beam to melt amorphous silicon for re-crystallization to form polysilicon. Although adjusting parameters of the laser beam may better the result of crystallization, the grain size and homogeneity of the annealed polysilicon are not only determined by the parameters of the laser beam; and the thickness of the chemical vapor deposition (CVD) film and the condition of rinsing with hydrogen fluoride (HF) may also impose influence on the final result of the laser annealing.
Referring to FIG. 1, a schematic view is given to illustrate the process flow of a conventional way of processing an amorphous silicon layer with laser annealing, wherein an amorphous silicon layer 100, which is of poor homogeneity (for having localized areas 102 of excessive film thickness), is only subjected to rinsing by spraying hydrogen fluoride 200 so that after the rinsing operation, a polysilicon layer 300 formed through laser annealing is obtained, but similarly presenting the issue of homogeneity.